1. Field of the Invention
This invention relates to a sliding-type DIP switch and, more particularly, to a sliding-type DIP switch suitable for mounting on a printed circuit board for the purpose of switching electrical circuitry.
2. Description of the Prior Art
An example of a conventional DIP switch of the above type is described in the specification of Japanese Patent Application Laid-Open No. 57-165926 and is illustrated in the sectional view of FIG. 3 (a). As shown, the DIP switch includes a box-shaped housing 2 insert molded about a set of fixed terminals 1, 1 each formed from a metal member die-punched in advance. When the insert molding operation is performed, a free end of each fixed terminal 1 is held firmly in position in a molding die and is formed into a contact portion 1a by the action of the die. This contact portion 1a is exposed above the floor surface of the housing 2, with the arrangement being such that the contact portions 1a, 1a of the respective fixed contacts 1, 1 oppose each other. A sliding contact 4 held by a slider 3 is slid back and forth between the opposing contact portions 1a, 1a to open and close these contacts, thereby performing a switching action.
Another example of the above-described DIP switch is described in the specification of Japanese Patent Application Laid-Open No. 56-45523 and illustrated in the sectional view of FIG. 3(b). As shown, the DIP switch includes a first base 12 in which a fixed contact terminal 11 is insert molded in advance, a second base 14 disposed on the first base 12 and in which a resilient movable contact terminal 13 having a movable contact 13a is insert molded in advance, and a slider 15 provided with a projecting portion 15a. The movable contact 13a is pressed against and released from the fixed contact terminal 11 by the projecting portion 15a, thereby closing and opening the switch.
The DIP switch having the structure shown in FIG. 3(a) is disadvantageous in terms of contact resistance and stability. Specifically, since the contact portion 1a of fixed terminal 1 is formed by the die for insert molding, it is necessary that a soft material capable of being molded be used as the material constituting the fixed terminal 1. Accordingly, self-actuation of the switch by relying upon its resilience is difficult, so that it is necessary to open and close the switch by a bridging or engaging-disengaging action performed by the separate contactor. Consequently, contact is made at a plurality of locations in series fashion, thus resulting in a large contact resistance. Furthermore, since the contact portion 1a is pressure molded by the molding die, contact instability is caused by the occurrence of scratches on the contact portion or by the adherence of dust or insulating substances such as the molding material to the contact partion. Another problem is the large number of component parts, which makes it difficult to assemble the switch.
The DIP switch having the structure shown in FIG. 3(b) is disadvantageous in that many man-hours of labor and a high manufacturing cost are demanded owing to the necessity of performing insert molding twice, namely once for the fixed contact terminal 11 and once for the movable contact terminal 13.